Mobile communications has evolved from an expensive service, used by relatively few people, to a commonly used and affordable service. Many people consider their mobile communications service as indispensable as land line telephone service. With the proliferation of mobile communication systems, there has been a demand for additional services besides mobile telephone service. Recently some service providers and system operators have begun to offer dispatch service in addition to telephone service, both types of service being supported by a single mobile communications device. Dispatch service is essentially a half duplex communication mode where users take turns speaking, similar to two way radio communication except the signal is carried over a land based network instead of directly from radio to radio. Just as each mobile communication device has an associated telephone number, so does it have an associated dispatch identification number.
It is also true that manufactures are designing more features into mobile communication devices. One feature that is gaining popularity is voice recognition for selecting a record from a memory of the mobile communication device. Typically a user stores the name and phone number of another party, or may have the number stored in one of a few speed call memory locations. When the user desires to call another party for which there is a record stored in the mobile communication device, the use activates voice recognition and speaks the party's name. The voice recognition algorithms maps the audio voice signal to, for example, a record identifier such as text, and uses this to locate a corresponding record in the memory. When the record is located, the associated phone number is retrieved and either the number is automatically dialed, or displayed so that the user can simply confirm it is the desired record.
Voice recognition is a relatively processor intensive operation. For a hand held, battery operated communication device, it is preferable to minimize the amount of processing done in completing tasks. There are numerous methods and algorithms for performing voice recognition, many of which, while powerful and typically are highly accurate, would require far more computing resources than is typically available in a cost sensitive product such as a mobile communication device. Therefore, the voice recognition techniques used are generally less accurate than higher accuracy versions used in, for example, desktop personal computers. Therefore, it is preferable if, in a mobile communication device, the voice recognition based record retrieval can be performed with the utterance of a single word. In communication devices that support only one mode of communication, i.e. telephone interconnect, only the name or speed dial number of the desired record needs to be uttered by the user. This limits the amount of processing that is necessary, and therefore allows the use of a less powerful voice recognition method.
However, in a mobile communication devices that support more than one type of communications modes, such as mobile telephony and dispatch calling, each record will typically have two numbers associated with it; one for a first mode of communication, such as dispatch or private dispatch calling, and a second number associated with a second mode of communication, such as mobile telephony. In employing voice recognition, the voice recognition would have to be given an indicator as to which communication mode is desired so that the appropriate number can be retrieved. This can be done by speaking the type of service in addition to the name of the party the user wishes to call. However, a two-word utterance is less likely to be accurately recognized; if a single word has a 90% probability of being recognized, two words together have only an 81% likelihood of being properly recognized (90% for each word). Therefore there is a need for performing voice recognition based record retrieval in a mobile communication device having more than one more of communication, without increasing the amount of voice information that needs to be processed.